Vibrators are used in many industrial applications where it is necessary to shake a structure or device with high amplitude vibrations. For example, vibrators are used to: shake screens for separating particles, such as crushed rock, by size; to vibrate bins and hoppers to prevent granular particles from "bridging" and to help granular particles flow; and to vibrate pieces of machinery, such as steam rollers. Various types of vibrators are currently available. All of these vibrators have disadvantages.
Many prior art vibrators cause vibration by turning an unbalanced rotor with an electric or hydraulic motor or by compressed air. These vibrators tend to be expensive because they require precision heavy-duty bearings and/or are inefficient at converting input energy into vibrational energy.
Water hammer is a phenomenon by which high intensity pressure pulses are produced in a confined body of flowing liquid when the flow of the liquid is suddenly blocked. Water hammer is generally undesirable, and can be destructive. Much effort is spent in the design of plumbing systems to avoid water hammer. Water hammer pressure pulses have not been previously used to drive industrial vibrators. The mathematics of water hammer are discussed in various texts on fluid mechanics including Fluid Mechanics (7th Edition) Victor L. Streeter and E. Benjamin Wylie, McGraw-Hill Book Company, 1979 and R. L. Daugherty and J. B. Franzini, Fluid Mechanics With Engineering Applications, pages 425-431 McGraw Hill Book Company, 1977.
Water hammer has been used to generate acoustic pulses for use in marine seismic exploration. For example, Baker et al., U.S. Pat. No. 3,376,949, Anstey, U.S. Pat. No. 3,536,157 Burg, U.S. Pat. No. 4,271,925, Bricout, U.S. Pat. No. 3,369,519 and Davis, U.S. Pat. No. 3,690,403 disclose underwater acoustic generators, also for use in underwater seismic exploration. Each of these devices use a deliberately created water hammer to produce a one-shot high amplitude burst of acoustic signals appropriate for geophysical seismic exploration. Akimoff, German patent No. 620,483, discloses a siren for broadcasting noise into air wherein the noise is generated by a series of water hammers in a pipe.
Bayhi, U.S. Pat. No. 4,396,088 discloses a generator of low power, low frequency acoustic waves for seismic exploration. The Bayhi apparatus modulates the flow of fluid flowing into an array of flexible sleeves at the frequency of the desired sound. Bayhi does not disclose the use of water hammer and is not designed for or adapted to shake industrial machinery or structures.